The announcement will pave the way to the formation of a new interim government within a month.

The de facto prime minister, Mahmoud Jibril, a technocrat who, despite having overseen the restoration of basic services to much of the country, is unpopular with both Islamists and revolutionaries for his links with the old regime of Gaddafi, is expected to stand down.

Many Libyans fear that will lead to a new power struggle between different regions and between Islamists and secularists, who in many cases have backgrounds in the West. Ali Tarhouni, an economist who left Libya in 1973 and was until this year an academic in the United States, has already declared himself a candidate.

Future

The National Transitional Council, which has effectively been the government of "Free Libya" since March, has been under great pressure to issue a formal declaration of victory as that was the agreed point from which the country's new political future could take shape.

In theory, the declaration will be followed in eight months by elections to a constitutional committee, which will oversee full, free elections after 12 months.

Mustafa Abdul Jalil, the chairman of the National Transitional Council, is due to make the announcement.

The choice of Benghazi was not explained, although the NTC has failed to keep repeated promises to move its headquarters there. The real reason is more likely to be that Tripoli has fallen under the control of Islamists, who lead the military council that has established a grip on the city.